It is well known in vehicle occupant restraint systems to provide an inflatable nylon-like fabric bag which is inflated by a gas generator. The gas generator for the passenger inflatable restraint system is preferably a cylindrical metal housing which contains chemicals such as sodium azide, and has ports therein through which hot gases generated by a chemical reaction within the cylinder may be exhausted into the inflatable cushion to inflate the cushion.
The prior art has recognized that the chemical reaction heats the cylindrical housing to a high temperature of perhaps 500.degree. C. The prior art patent U.S. Pat. No. 4,944,527 has taught the provision of a heat shield of stamped steel construction is formed in a cylindrical shape and has an open end through which the gas generator is inserted. Portions of the heat shield contact with the gas generator to positively locate and mount the gas generator within the heat shield, but this area of contact is preferably minimized so that the more substantial portions of the heat shield are spaced away from the gas generator to minimize the conduction of high temperature from the gas generator to the heat shield. The cylindrical walls of the heat shield are preferably slotted to define flaps which unfold in response to the flow of high temperature gas so that the flaps permit the free flow of the hot gas from the gas generator into the air bag and also spread the inflatable cushion fabric away from proximity with the hot gas generator.
The present invention recognizes that high temperatures caused by the chemical reaction within the gas generator may be conducted through the heat shield, particularly those portions of the heat shield which directly contact with the end of the gas generator cylinder. This high temperature conduction to the heat shield may tend to pyrolize the nylon-like fabric of the inflatable cushion and thereby introduce particulate matter into the occupant compartment.